A double-labeled immunofluorescent test will be employed with rhodamine-labeled goat anti-rabbit IgG, rabbit antisera to oral filamentous bacteria and fluorescein-labeled goat anti-human IgG, IgA, IgM and C3. With these reagents, the specific subgingival flora coated in vivo with immunoglobulins and complement will be examined. Immune complexes in human gingival tissue will also be studied and the average concentration of such complexes in inflamed gingival tissue will be evaluated for their ability to cause alveolar bone loss.